What did you do the above for?
I think your confusing steps. There is no code modifications needed. you just need to take care of each issue one at a time.
If you upgrade your VB
naturally you then UPDATE Photopost to use VB3 not VB2 and then when correctly able to login you then UPGRADE THE SOFTWARE TO THE NEW 4.8.5 VERSION
You were trying to do two things at once and confused yourself on what steps come where and then think there is a problem when there is not.
The cookie variables are no longer stored in the config file but in the database. and no matter what if you switch integration types of course you would need to switch the type in mysql if you cant login.